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How to troubleshoot degraded connectivity from a host to a filer

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Category:
data-ontap-dsm-for-windows-mpio
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san
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Applies to

SAN Protocol

Description

Multipathing (MPIO) software allows the hosts to maintain multiple paths to a LUN. Paths to the NetApp node where a LUN resides are considered "Active/Optimized" while paths through the node's HA partner are considered "Active/Un-Optimized". The exact terminology may vary depending on the host operating system and multipath drivers. Certain scenarios can lead to one or more paths being inaccessible or otherwise unavailable for I/O. Depending on which paths are unavailable, the host may experience performance degradation, especially if there are no other "Active/Optimized" paths remaining. 

Path states are determined by the node that currently owns a LUN using ALUA. When a takeover occurs, the paths through the node that assumes ownership of it's partner's LUNs will become "Active/Optimized".

Example of a path failure in RedHat 'multipath -ll' output: 

# multipath -ll
mpath0 (360a9800043346441464a44424c746e54)
[size=10 GB][features="1 queue_if_no_path"][hwhandler="0"]
_ round-robin 0 [prio=8][active]
_ 0:0:0:0 sda 8:0   [failed][faulty]
_ 1:0:0:0 sdi 8:128 [active][ready]
_ round-robin 0 [prio=2][enabled]
_ 0:0:1:0 sde 8:64  [active][ready]
_ 1:0:1:0 sdm 8:192 [active][ready]

RedHat '/var/log/messages' Examples:

Jun 22 15:55:54 rhel1 multipathd: Lun1: sdcr - tur checker reports path is down
Jun 22 15:55:54 rhel1 multipathd: checker failed path 69:240 in map Lun1
Jun 22 15:55:54 rhel1 multipathd: Lun1: remaining active paths: 3
Jun 22 15:55:54 rhel1 kernel: device-mapper: multipath: Failing path 69:240.


VMware 'vmkernel' Examples:

2017-11-30T07:17:41.351Z cpu15:33143)WARNING: NMP: nmp_DeviceRequestFastDeviceProbe: NMP device "sym.029025256531353837" state in doubt; requested fast path state update...
2017-11-30T07:17:41.351Z cpu15:33143)WARNING: ScsiPath: 4507: Path vmhba2:C0:T0:L55 is being removed
2017-11-30T07:17:41.351Z cpu15:33143)WARNING: ScsiPath: 6117: Remove path: vmhba2:C0:T0:L55


Windows 'System Event Log' Examples:

Information    10/31/2017 4:39:33 PM    mpio        46       None    Path 1000001 was removed from \Device\MPIODisk2 due to a PnP event. The dump data contains the current number of paths.
Information    10/31/2017 4:39:33 PM    ontapdsm    61070    None    Path ID 01000001 was removed.
Warning        10/31/2017 4:39:33 PM    ontapdsm    61054    None    Path ID 01000001 has failed and 02000101 will be used instead.
Error          10/31/2017 4:39:33 PM    ontapdsm    61142    None    Path ID 01000001 has failed.


Note: The exact log entries may vary depending on the operating system version and how multipathing is configured. 

 

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